This invention relates to pumping systems and more particularly to pumping systems that draw samples from a source of liquid.
It is known from U.S. Pat. No. 4,415,011 to Douglas M. Grant, issued Nov. 15, 1983, and from U.S. Pat. No. 4,660,607 to Carl D. Griffith, issued Apr. 28, 1987, to pump liquids from a liquid source through a peristaltic pump into sample containers. In such system, the liquid is pumped through a flexible tube, the location of the liquid in the tube is sensed and it is metered into sample containers. The tube is subjected to flexing by rollers at a rate intended to deposit a predetermined sample volume into preprogrammed containers arranged in a sample tub. A distributor may move a nozzle over the appropriate sample bottle to deposit the sample therein. The distributors usually follow one predetermined path.
In the, prior art samplers of this type, the peristaltic pumps are generally mounted horizontally with a horizontal axis of rotation for the roller assembly and fasteners such as bolts or screws must be removed to obtain access to the interior of the pump. The distributor only follows a continuous path and stops at mechanically fixed positions to deposit samples. Equipment used for triggering the taking of samples such as flow meters in stand alone equipment for such measurements.
These prior art samplers have several disadvantages such as for example: (1) under some circumstances, the tubes may travel laterally out of position within the peristaltic pump, resulting in a decrease in efficiency and increase in wear on the tube; (2) the pump may be unable to pump at the desired flow rate when there is a large head of pressure; (3) the tube within the pump may be subject to excessive wear; (4) it is difficult to change the peristaltic pump tube; (5) there may be occasions in which the outlet port of the sampler does not align in a satisfactory manner with the container to provide liquid therein; (6) there is insufficient flexibility in the movement of the distributor; (7) the samples may under some circumstances be tampered with to avoid detection of of some water conditions; and (8) the equipment used in cooperation with the sampler is excessively bulky and expensive.